Thermal spray coatings, also known as thermal spraying or spray metallizing, are a group of surface coating processes used to apply protective or functional coatings onto various substrates. These coatings are created by heating and propelling a feedstock material, such as powder or wire, onto the substrate surface, where it forms a coating upon impact.
The thermal spray process involves the following key steps:
Preparation: The substrate surface is prepared by cleaning, roughening, and sometimes applying a bond coat or primer layer to enhance adhesion between the coating and the substrate.
Feedstock Material Selection: Different types of feedstock materials can be used in thermal spray, including metals, alloys, ceramics, composites, and polymers. The choice of material depends on the desired coating properties and the application requirements.
Heating: The feedstock material is heated to a molten or semi-molten state using various heat sources, such as combustion flames, plasma arcs, or electric arcs. The heat source melts or softens the feedstock particles for the coating process.
Propulsion: The molten or semi-molten feedstock particles are propelled towards the substrate using a spray gun or nozzle. This can be achieved by a combination of compressed air, gas, or other gases, depending on the specific thermal spray process.
Impact and Bonding: When the feedstock particles reach the substrate surface, they solidify and bond, forming a coating layer. The impact velocity and energy of the particles help ensure good adhesion between the coating and the substrate.

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